What is 802.11ac WiFi, and how much faster than 802.11n is it?

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If you’re looking for faster WiFi performance, you want 802.11ac — it’s as simple as that. In essence, 802.11ac is a supercharged version of 802.11n (the current WiFi standard that your smartphone and laptop probably use), offering link speeds ranging from 433 megabits-per-second (Mbps), all the way through to several gigabits per second. To achieve speeds that are dozens of times faster than 802.11n, 802.11ac works exclusively in the 5GHz band, uses a ton of bandwidth (80 or 160MHz), operates in up to eight spatial streams (MIMO), and employs a kind of technology called beamforming. For more details on what 802.11ac is, and how it will eventually replace wired gigabit Ethernet networking at home and in the office, read on.

How 802.11ac works

Years ago, 802.11n introduced some exciting technologies that brought massive speed boosts over 802.11b and g. 802.11ac does something similar compared with 802.11n. For example, whereas 802.11n had support for four spatial streams (4×4 MIMO) and a channel width of 40MHz, 802.11ac can utilize eight spatial streams and has channels up to 80MHz wide — which can then be combined to make 160MHz channels. Even if everything else remained the same (and it doesn’t), this means 802.11ac has 8x160MHz of spectral bandwidth to play with, vs. 4x40MHz — a huge difference that allows it to squeeze vast amounts of data across the airwaves.

To boost throughput further, 802.11ac also introduces 256-QAM modulation (up from 64-QAM in 802.11n), which basically squeezes 256 different signals over the same frequency by shifting and twisting each into a slightly different phase. In theory, that quadruples the spectral efficiency of 802.11ac over 802.11n. Spectral efficiency is a measure of how well a given wireless protocol or multiplexing technique uses the bandwidth available to it. In the 5GHz band, where channels are fairly wide (20MHz+), spectral efficiency isn’t so important. In cellular bands, though, channels are often only 5MHz wide, which makes spectral efficiency very important.

802.11ac also introduces standardized beamforming (802.11n had it, but it wasn’t standardized, which made interoperability an issue). Beamforming is essentially transmitting radio signals in such a way that they’re directed at a specific device. This can increase overall throughput and make it more consistent, as well as reduce power consumption. Beamforming can be done with smart antennae that physically move to track the device, or by modulating the amplitude and phase of the signals so that they destructively interfere with each other, leaving just a narrow, not-interfered-with beam. 802.11n uses this second method, which can be implemented by both routers and mobile devices. Finally, 802.11ac, like 802.11 versions before it, is fully backwards compatible with 802.11n and 802.11g — so you can buy an 802.11ac router today, and it should work just fine with your older WiFi devices.

The range of 802.11ac

In theory, on the 5GHz band and using beamforming, 802.11ac should have the same or better range than 802.11n (without beamforming). The 5GHz band, thanks to less penetration power, doesn’t have quite the same range as 2.4GHz (802.11b/g). But that’s the trade-off we have to make: There simply isn’t enough spectral bandwidth in the massively overused 2.4GHz band to allow for 802.11ac’s gigabit-level speeds. As long as your router is well-positioned, or you have multiple routers, it shouldn’t matter a huge amount. As always, the more important factor will likely be the transmission power of your devices, and the quality of their antennae.

How fast is 802.11ac?

And finally, the question everyone wants to know: Just how fast is WiFi 802.11ac? As always, there are two answers: the theoretical max speed that can be achieved in the lab, and the practical maximum speed that you’ll most likely receive at home in the real world, surrounded by lots of signal-attenuating obstacles.

The theoretical max speed of 802.11ac is eight 160MHz 256-QAM channels, each of which are capable of 866.7Mbps — a grand total of 6,933Mbps, or just shy of 7Gbps. That’s a transfer rate of 900 megabytes per second — more than you can squeeze down a SATA 3 link. In the real world, thanks to channel contention, you probably won’t get more than two or three 160MHz channels, so the max speed comes down to somewhere between 1.7Gbps and 2.5Gbps. Compare this with 802.11n’s max theoretical speed, which is 600Mbps.

In Anandtech’s 2013 testing, they paired a WD MyNet AC1300 802.11ac router (up to three streams), paired with a range of 802.11ac devices that supported either one or two streams. The fastest data rate was achieved by a laptop with an Intel 7260 802.11ac wireless adapter, which used two streams to reach 364 megabits per second — over a distance of just five feet (1.5m) At 20 feet (6m) and through a wall, the same laptop was the fastest — but this time maxing out at 140Mbps. The listed max speed for the Intel 7260 is 867Mbps (2x433Mbps streams).

In situations where you don’t need the maximum performance and reliability of wired GigE, though, 802.11ac is very compelling indeed. Instead of cluttering up your living room by running an Ethernet cable to the home theater PC under your TV, 802.11ac now has enough bandwidth to wirelessly stream the highest-definition content to your HTPC. For all but the most demanding use cases, 802.11ac is a very viable alternative to Ethernet.

The future of 802.11ac

802.11ac will only get faster, too. As we mentioned earlier, the theoretical max speed of 802.11ac is just shy of 7Gbps — and while you’ll never hit that in a real-world scenario, we wouldn’t be surprised to see link speeds of 2Gbps or more in the next few years. At 2Gbps, you’ll get a transfer rate of 256MB/sec, and suddenly Ethernet serves less and less purpose if that happens. To reach such speeds, though, chipset and device makers will have to suss out how to implement four or more 802.11ac streams, both in terms of software and hardware.

We imagine Broadcom, Qualcomm, MediaTek, Marvell, and Intel are already well on their way to implementing four- and eight-stream 802.11ac solutions for integration in the latest routers, access points, and mobile devices — but until the 802.11ac spec is finalized, second-wave chipsets and devices are unlikely to emerge. A lot of work will be have to done by the chipset and device makers to ensure that advanced features, such as beamforming, comply with the standard and are interoperable with other 802.11ac devices. For more, read How to boost your WiFi speed by choosing the right channel.

Sebastian Anthony wrote the original version of this article. It has since been updated with new information.

I consistently get 353 Mb/s between three walks in a nyc apartment building between my buffalo ac router and media bridge, so I don’t get what the big deal about waiting for non draft ac routers is.

Mangap

as long as it is upgradeable through firmware I hope still OK

some_guy_said

“will eventually replace wired gigabit ethernet networking at home and in the office, read on.”

This is where you lost me. 90% of what’s still wired in the home is wired in because of inherent limitations of using radio waves.

150/300mbps is not holding anyone back at home, unless they’re doing direct computer to computer file transfers, or have a ludicrous number of devices working on the network simultaneously.

The primary benefit of this will be for public networks that already use wifi.

Michael Lippert

OK for now, sure you are mostly correct. Although there are some of us w/ media servers at home, where having a gigabit wired connection is actually noticeable, the majority of households care only about connecting to the internet and are limited by the bandwidth provided by their internet provider.

However, Google fiber provides a gigabit internet connection, and if we could kick the broadband monopolies off their ass to provide bandwidths comparable to many other places in the world, more of us might eventually have faster internet connections. I’m not sure how that bandwidth will get used, but I’m sure it will.

some_guy_said

While I agree in eventuality, there is currently little to no use to having more than 25-50 mbs for a home user. Even the few applications that ‘could’ use it are generally hampered by issues upstream of your home connection. (how often does any site offer DL’s over a few mb/s? The biggest hogs, netflix and some games, typically top out at 5-7 mb/s) Current wifi is far more powerful than needed even to stream 4k.

So I agree in theory, and this is something that will be eventually needed, but it’s usefulness is very limited for at least 5 – 10 years, due to all the other bottlenecks and lack of a killer app – or a need for one.

I just replaced my old g router and doc2.0 modem. Not because I needed more speed, but because the old ones were 12 years old and burning out. Only a very connected large household would have a compelling consumer need for even today’s wifi tech. So there’s a ways to go.

rrdonovan

Ah yeeessss, radio waves. Have you ever been in a small room with 30 to 40 laptops running wirelessly? It is like bees swarming over your face. This phenomena occurred when I set up a small lab with a bunch of laptops for elementary students. The teachers were afraid to enter because of this buzzing in the face effect. I had to half the number of laptops for this to effect to minimize. Just how many radio waves, intensity, frequency, etc. does it take to harm human cells? This needs to be studied. I tried to get the university where I worked to start a study on radio wave effects on the human body, but nobody was interested. I also don’t work there anymore……..

Master Rod

some_guy_said

I can’t tell if you’re serious. But I would point that you’re blasted by electromagnetic radiation all the time. It’s called…light.

And seeing as radio waves have less energy than…light, and are non-ionising, the potential for harm is pretty low.

While large amounts of energy at a very specific wavelength – Such as 2.45 Ghz, can cause a type of resonant frictional heating in a water molecule…that’s just what it causes – heat – in a microwave.

As for your computer lab…It could be one of many biomechanical interactions with the radio waves, or possibly something else. There are lots of unknown variables to this secondhand story that I can’t comment on.

rrdonovan

You can’t comment on? Ah! so you know about this. Well, this is no second hand story. I built the temporary lab. The kids thought it was funny, the teachers did not. It really was an odd sensation……..

some_guy_said

I can’t comment on your particular experience because of all the the unknown variables, the fact that YOUR story is second hand to me, and I am only vaguely aware of some of the phenomenons that could be involved.

I can’t reasonably comment on it, because I do not have enough knowledge or information to form a valid opinion on your particular experience.

I can’t comment on it, because I don’t (and can’t) know enough about it. Does that make sense to you?

LT Fang

Since no number of radio wave emitting sources can actually increase the frequency of the radio waves……… luckily Einstein has figured out 100 years ago increase in energy of radio waves, no matter how much energy, cannot increase the frequency. Without an increase in frequency, no amount of intensity has a single photon energetic enough to have any effect on us.

Mangap

Now we need standard, where access point can be used by many people. example on stadium where thousands people there. now it is difficult to implement access point for this situation

Joel Detrow

You mean IPV6?

Mangap

No. Current Access point can only handle around 30 user. (theory say 100) when we use it on stadium/ event with 1000-10.000 people there we can not use normal access point. we need special ones

rrdonovan

“…and how it will eventually replace wired gigabit ethernet networking at home and in the office,…”

Just like contraceptives will replace abortion, right?! This writer know not of what he speaks. There are reasons for direct hardware connect. Security is one of them, speed is another. The only thing that will replace copper is most probably fiber optics, not wireless.

You know technology is similar to Wall Street. Every so often, a new craze debuts. OK, for the weak minded out there, let’s take tablets. The company’s producing these products are fleecing the public, their fanboys, and every nut job that believed the pitch that tablets would supersede desktops and laptops. What we got were shitty underpowered, featureless, products with no upgrade path. A lot of people bought into this. This let down brought the companys to say “Oh, wait till next year, we have a better tablet”. The problem is that the next tablet may have just one improvement rather than a comprehensive one. Ergo, they milk the public for all they can get. The sheeple just keep begging for more.

I want a quad core tablet with several usb ports. I want a docking station with external monitor ports. I want an 8 hr. battery life with at least 4 gig of ram. I want it to run Linux or be at least X86 compatible. Don’t even start to talk to me about Android. It should have at least a 160 gig hard drive, or at the very minimum a 128 gig SSD drive (Much better for overall speed). You hear me companys. Put your money where your mouth is, and provide us with something worthwhile. This nickel and dime stuff you are peddling is crap!

Our most recent trend is “The Cloud”. Oh, My, God! If Washington is getting hacked left and right, what! You want to dangle a carrot of valuable data in a cloud for everyone to see? WTF! Are you insane? These Clouds are getting hacked left and right. Granted, maybe for data that has no significance to anybody, stuff that is easy to get to with just about any device. But credit card numbers, bank accounts, corporate data? No way. If your CIO believes in this Cloud business, get rid of him quick before your shits out in the street.

Sorry about some of my language. I’m just passionate about what I write. It is just hard to make people understand certain technological concepts with out them falling prey to this technology black hole every so often. As for these technical journalists, most of them should be writing about little Suzy’s party, or some such nonsense. Leave the technology writings to us Technologist who have been around the block a few times.

Master Rod

ps. smart watches, and glasses are coming. Look out…….

http://www.mrseb.co.uk/ Sebastian Anthony

Thanks for taking the time to comment!

I actually have a networking background, so I understand this topic fairly well. If you read the story, I note that GigE will still have its uses. For the vast majority of use cases, though, 802.11ac (and 802.11n, to be honest) are more than good enough.

As for the rest of your treatise… I can kind of see your point. Bear in mind that the PC is actually dying because of tablet sales, though. I don’t think tablets are just a flash in the pan.

rrdonovan

Good Point Sebastian! I stand corrected. Also, Yes you are correct in tablets replacing the PC eventually. It is just the time element and the PC company’s way of hacking out this piece meal not just ready for prime time hardware. Again, If I had an 8″ tablet phone or phablet, with the specs I requested earlier, I could readily see the end of PCs and laptops. As for Servers? Well, that is another story. Oh, and keep writing! After a 2nd reading, I find that you too are passionate about technology. “Onward, through the fog”. Enjoy!

Master Rod

preilly2

Sebastian, thank you for the very thorough coverage of the new standard and what we can expect from it. But seriously, you’re a young guy living in the UK and you already own a ‘massive’ detached house and gardens? Technology journalism must pay a lot better than I thought it did!

So it sounds like it might be best to wait until the next wave of chipsets come out… I dont want to invest $200 only to have the next wave come out 2 years later.

Singh1699

Do you even need the speed of n at this point? G is outdated as you can get unlimited 50mb+ dl for under 50 per month in Canada. But ven n150 is fine and most stuff is n300.

Singh1699

I’d get an n300+ router with solid ddwrt support that is fairly robust as my old g would overheat tormenting.

Marin Knežević

Am I missing something or there are multiple places in the article where there is 802.11n written instead of 802.11ac?! Starting from “…this means that 802.11n has 8x160MHz of spectral bandwidth…” and so on in several places later in the article.

http://www.securitycamera-ny.com/ Mark in NY

is that 802.11ac router very expenience?

https://plus.google.com/+Intercomrepairny/about?hl=en ryan

the router going cheaper now

Adrian Alphamale Levy

Good article Sebastian and funny comments guys.

Zachary Varley

I’m trying to understand this topic of ac vs. n (knowing little about computers). It says above “Finally, 802.11ac is fully backwards compatible with 802.11n and 802.11g”, and I’m wondering how 802.11n stands, not necessarily becoming obsolete, but with 802.11ac becoming standardized and n being less usable/compatible.

I’m currently comparing refurbished macbook pros (which provide only 802.11n) vs a new one with 802.11ac. I will be uploading lots of photos and videos (a bit less frequently) so I’m trying to get a grasp on the matter, and how it will ACTUALLY affect me.

Also some_guy_said mentioned download speed/restrictions, pointing that most sites are limited to a few mb/s, with bigger hosts providing slightly more. Assuming this is true(?) are upload speeds limited in a similar way?

jone

what is multi-user MIMO?

AK

Can’t see it ever completely replacing cabling. Maybe for most home users, but then again the old wifi standards are already sufficient for most home users so it wouldn’t make much difference. For people who are serious about their connections I don’t think you can replace the reliability, stability, and uncontendedness (not sure how to phrase that!) you get with wired.

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